French published patent specification FR 1 295 138A describes and shows an arrangement of the kind described above, in which the screen wiper element or elongate member has a transverse cross section in the general form of an inverted U, which defines a longitudinal recess in the lower face of the screen wiper arm, which is open towards the swept surface, with the said recess receiving a flexible feed pipe in which the washing liquid flows, and which is arranged to supply with this liquid at least one spray device for spraying the liquid on to the swept surface, this spray device being disposed (for example) close to one free end of the screen wiper arm.
An advantage of that design is that it enables the flexible feed pipe to be protected, and it reduces the size of the liquid feeding system, while preserving good aerodynamic features of the screen wiper arm. However, the fitting of the flexible feed pipe into its housing makes it necessary to employ appropriate fastening devices, such as collars, arranged at various points on the screen wiper arm. This design thus calls for a relatively large number of costly components, and its assembly is particularly difficult to carry out using automatic assembly equipment.
In another known design that has been proposed, the flexible feed pipe is made integrally by moulding in the body of the screen wiper element or elongate member, the latter being again, in particular, the screen wiper arm. This arrangement avoids having to provide the feed pipe as a separate component, but it is particularly complex to achieve, and the moulding techniques which are necessary are too expensive.